PROJECT SUMMARY Vulnerability to the deleterious mood effects of normal changes in reproductive hormones is a likely underpinning to reproductive mood disorders. The menopause transition (MT) is associated with pronounced hormonal variability (within the context of relative E2 deprivation) and substantially increased risk for clinically impairing anxiety and anhedonia. Anxiety is characterized by cognitive bias to interpret ambiguous stimuli in a threat-related manner. Anhedonia can be defined by decreased motivation to approach rewards. The neurobiologically-based constructs of ?threat reactivity? and ?approach motivation? provide a framework for studying the pathophysiology of the clinical impairment experienced by 25% of women in the MT. Although the causes of affective symptoms in the MT remain unknown, severe life stress proximate to the MT is a strong predictor. Framed within a diathesis-stress model, the primary objective of this research is to determine the pathophysiological mechanisms of estradiol (E2) in the clinical anxiety and anhedonia seen in the MT. Specifically whether E2 variability or E2 levels predict exaggerated hypothalamic-pituitary-adrenal (HPA) axis reactivity and impaired recovery to stress and, in turn, deficits in behavioral indices of threat responsivity and approach motivation and symptoms of anxiety and anhedonia. The secondary objective of the research is to use a hormonal manipulation as a mechanistic probe to stabilize E2 variability in premenopausal ranges and determine if: a) HPA axis reactivity/recovery represents a biomarker of behavioral and symptom responses to E2 stabilization; b) whether recent severe life stress predicts the HPA axis response to hormone stabilization. A total of 170 women in the early or late MT who are eligible for the hormonal probe will be recruited to reflect the full continuum of anxiety and anhedonia symptoms based on self-report to the State-Trait Anxiety Inventory and the Snaith-Hamilton Pleasure Scale, respectively. However, we will over-represent the clinically impairing end of the anxious and anhedonic phenotype (75% of the sample). Over an 8-week baseline, anxiety and anhedonia symptoms and serum E2 measured by liquid chromatography-tandem mass spectrometry (LC- MS/MS) will be assessed on a weekly basis. At baseline week 8, HPA axis (plasma cortisol and ACTH) response to the Trier Social Stress Test and behavioral measures of threat responsivity (via Dot-Probe task) and approach motivation (Effort Expenditure for Rewards Task ?EEfRT?) will be determined. Using transdermal E2 as a pharmacological probe to stabilize variability of E2 in premenopausal ranges, women will then be randomized to transdermal E2 (0.10 mg) or placebo for 16 weeks. This is not a clinical efficacy trial. We will use an RCT design with a hormonal manipulation in order to investigate the pathophysiologic role of E2 variability (or E2 levels) in HPA axis dysregulation and, in turn, threat responsivity and approach motivation. Serum E2 will be assessed weekly during weeks 9-16, and HPA axis reactivity to stress and behavioral responses to the Dot-Probe and EEfRT tasks will be assessed every four weeks during the 16 week probe.